Protective gas masks for the human face are well known. People wearing the gas masks often have a need to communicate with one another, particularly in emergency situations. Several communication systems have been developed for this purpose.
For example, Berman U.S. Pat. No. 3,314,424 includes a microphone inside the mask and an amplifier assembly outside the mask, with an electrical cable extending therebetween and passing through a sealed grommet in the mask. Bergman U.S. Pat. No. 3,243,511, assigned to the same company as the Berman patent, shows substantially the same mask as the Berman patent with the amplifier circuit being disclosed.
Lewis U.S. Pat. No. 3,180,333 discloses a gas mask communication system including a generally U-shaped holder connected to the mask. Preferably, the holder includes the amplification speaker in one end portion thereof and the batteries for operating the speaker system in the other end portion thereof. The batteries and amplification system are connected in circuit with a microphone inside the mask adjacent the user's mouth. Additional or parallel speakers can be plugged into the Lewis mask communication system including, for example, a speaker attached to the belt of the wearer.
Ingels U.S. Pat. No. 4,508,936, Bloom U.S. Pat. No. 2,953,129 and Duncan U.S. Pat. No. 2,950,360 disclose face mask communication systems having a microphone carried in the face mask and an amplifier or speaker externally coupled to the face mask for support elsewhere, such as around the waist of the user. These voice communication systems for masks have several disadvantages. First, the attachment of the amplifier or speaker to the waist adds weight and bulk to the unit and partially limits the mobility of the wearer. Second, the person wearing the mask often turns his head during an emergency situation to talk, but the amplifier or speaker on his waist does not simultaneously turn since his body does not turn. Thus, the wearer is attempting to project his voice in one direction but the voice is actually being transmitted in a different direction. By having the face and amplifier or speaker potentially as much as 90.degree. apart in direction, the efficiency and effectiveness of the voice transmission and projection is diminished.